North American River Otter
An adult can weigh between 11 and 30 lbs. Males tend to be larger than females.
They average in 26 to 46 inches in body length and 12 to 20 inches in tail length.
In captivity, the average lifespan is 21 years. In the wild, it is 8 to 9 years.
They consume fish, crustaceans, reptiles and amphibians, birds, insects, and mammals.
They are capable of consuming 2.2 to 3.3 lbs of fish per day. During the winter and spring, they have a tendency to prey upon crayfish. Reptiles and amphibians are easier to prey on in the spring and summer. Mammals are not the main dietary component. They will prey on smaller mammalian species, such as muskrat, voles, cottontails, etc.
River otters are generally nocturnal, while sea otters are diurnal.
Breeding season is from December to April. Female estrus lasts about a month per year, and true gestation lasts 61 days. River otters delay implantation for at least eight months.
This distinguishes the North American River Otters from their European counterparts.
The young are born between February and April. Birthing process can take three to eight hours.
Litter size can be up to five pups but tends to average three pups. Otter young are called pups or kits.
The young are born fully furred, blind, and toothless. The kits open their eyes after 30-38 days.
The newborns start playing at five to six weeks and begin consuming solid food at 9-10 weeks.
The otter pups are weaned at 12 weeks. They are at adult weight at 3 to 4 years of age.
Females raise the young alone. Mothers introduce the pups to water at 2 months of age, this is when their coats are completely grown in. Even though they are capable of sustaining themselves once they leave the den, otters tend to stay in family groups. These groups are usually the mother and young, but sometimes includes the father. They will stay in these groups until the following spring.
Yearlings will venture out in search of their own territories, females usually venture farther than the males. The females tend to be more territorial than males. Many young males will join established male groups.
The river otter is a semi-aquatic mammal. It establishes a burrow close to the water’s edge.
The den usually has many tunnel openings, one of which allows the otter to enter and exit the body of water.
Their right lung is larger than the left, having four lobes compared with two for the left. It is believed to be adaptive for underwater swimming.
An adult river otter has 36 teeth.
They travel up to 26 miles in one day.
Beavers are very important friends to otters, they make the ideal habitats for them. Often beavers and otters share the same ponds or streams.
They can swim at speeds of about 6 miles per hour. Underneath the water surface, they swim at 3 to 4 miles per hour.